U.S. Pat. No. 4,636,147 discloses a chain saw having a lubricating oil pump. The pump piston of this lubricating oil pump is moved by means of a control member which lies against a stroke cam of the pump piston. The pump piston is axially reciprocated by the rotation thereof. If it is not necessary to pump the lubricating oil, then the control member is manually lifted from the stroke cam so that the pump piston can no longer undergo any pumping movement thereby interrupting the pumping action of the lubricating oil pump.
The lubricating oil pump is switched on during the operation of the saw chain since lubrication of the saw chain running in the guide groove is then desired. Because of the continuous operation of the oil pump, this leads to the condition that the oil pump continues to pump oil into the guide groove even during idle when the saw chain is at standstill so that excess oil is expelled in an uncontrolled manner.